It has been four years since BMW unveiled its ‘batmobile’ i8 Spyder concept car.

Now, reports suggests the car manufacturer could be about to launch a convertible version of the vehicle at the CES technology show in January.

And according to BMW CEO Harold Krueger, a production version of the much-anticipated i8 Spyder convertible concept may also make its debut shortly after.

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It has been four years since BMW unveiled its ‘batmobile’ i8 Spyder concept car. Now, reports suggests the car manufacturer could be about to launch a convertible version of the vehicle at the CES technology show in January. Pictured is an artist's impression of what the car could look like

BMW i8: KEY STATISTICS

Two-door sports car with seating for two adults and two children

360bhp

1.5-litre, 3-cylinder turbocharged engine

96 kilowatt/130bhp electric motor

0-60mph in 4.4 seconds

Top speed: 155mph

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A coupe version of the i8 has been sitting in showrooms for some time.

Currently, it delivers a maximum 362 horsepower and an electric range of around 23 miles (37km).

The i8 Spyder convertible is expected to preview some of the changes that will appearing in the mid-cycle update of the i8.

These could include an improved visual design and better power and range, according to a report in Auto Express.

The i8 Spyder will share the same hybrid petrol/electric powertrain and the i8.

The launch of the convertible version has been delayed largely because of technical difficulties.

In December 2013, officials revealed the car was presenting "major challenges" to its engineers.

These challenges included translating the carbonfibre-reinforced plastic body shell construction of the i8 into a convertible format.

Earlier this year, BMW also revealed a modified i8 coupe that runs on hydrogen.

It can travel 300 miles on one tank of hydrogen, with refuelling taking about five minutes.

New bodywork, aerodynamic wheels, and matte black paint make it look like stealth jet fighter - or a batmobile.

The two-door coupé relies on carbon fibre construction to keep its weight down and also features an aerodynamic package developed at BMW's wind tunnel in Munich.

Energy for the fuel stack is provided by cryogenically stowed hydrogen contained in a cylindrical tank mounted down the centre line of the car's platform and oxygen provided by cooling air.

The fuel stack subsequently provides electricity to run a rear-mounted electric motor, with the only emissions being water.

BMW could also introduce a power upgrade using a larger internal combustion engine and a higher-capacity battery. Experts suggests a 2.0-liter turbo four could be used in both the convertible, coupe and the roadster

Earlier this year, BMW also revealed a modified i8 coupe that runs on hydrogen. It can travel 300 miles on one tank of hydrogen, with refuelling taking about five minutes

'It converts the gaseous hydrogen contained in the storage tank into electric power and water vapour,' the firm said.

'The vehicle’s high-voltage battery serves as an energy storage unit and can therefore be considerably smaller – with a net capacity of around one kilowatt hour – than in battery-electric concepts.

'Storing hydrogen in a cryogenic pressure vessel can, depending on the type of vehicle, allow an operating range comparable with that of conventional vehicles powered by combustion engines.

'Filling up the hydrogen storage tank takes a similar amount of time as refuelling a petrol or diesel tank.'

Power is put at 242bhp – 115bhp less than the petrol-electric hybrid system used by the production i8.

However, BMW stresses car will deliver 'instantaneous power delivery and impressive dynamics', and refuelling in under five minutes.

Some have compared the BMW i8 Spyder to the Batmobile for its sleek design and futuristic features